Carburetor accelerating pump



Aug. 8, 1944.- w WEBER 2,355,346

GARBURETOR AGCELERATING PUMP Filed March 13, 1942 40 ATTORNEY Patented Aug. 8, 1944 v Walter H. Weber,

trolt Lubricator Detroit, Mich, alsignor to 'De- Company, Detroit, corporation of Michigan Mich. a

Application March 13, 1942, Serial No. 434,485

This invention relates to new and useful improvements in carburetor pumps for supplying supplemental fuel to an internal combustion engine and, more particularly, to thermostatic means for controlling the quantity of supplemental fuel.

An object of the invention is to provide thermostatic means which will positivelylimit the quantity of supplemental fuel discharged by the pump.

The invention consists in the improved construction and combination of parts to be more fully described hereinafter and the novelty of which will be particularly pointed out and distinctly claimed. o

In the accompanying drawing to be taken as a part of this specification there are fully and clearly illustrated several preferred embodiments of the invention, in which drawing:

Figure 1 is a diagrammatic view in vertical section of a carburetor and fuel supply pump embodying the invention, and

Fig. 2 is a diagrammatic view in section of another form of carburetor and fuel supply D p Referring to the drawing by characters of reference, the carburetor of Fig. 1 has a casing l with a mixture passageway 2 therethrough in which is positioned a converging diverging throat member 3, such as a Venturi tube. The passageway 2 has a main air inlet I and a mixture outlet 5 and flow therethrough is controlled by a throttle valve 6.. Discharging into the pas sageway 2 adjacent the throat of the Venturi tub there is a main fuel nozzle 1 which is supplied with fuel from the usual constant level chamber or reservoir 8 containing the usual float operated inlet mechanism 9 which serves to maintain the fuel level substantially constant at the line L-L.

Positioned adjacent the carburetor and supported in any suitable manner as from the casing I there is a fuel supply pump l0 having a casing H containing a fluid displacement member l2 supported for suction and pressure or discharge strokes. The casing II has base and covermembars which clamp .therebetween the periphery of the member l2 which is a flexible resilient diaphragm of any suitable oil resisting rubberlike material. The member I 2 cooperates with the casing base member to provide a pump chamber if having a check valve controlled inlet ll communicating through a conduit ll with the float chamber 8 below the liquid level therein. The

pump chamber I 3 has a check valve controlledoutlet II which discharges into the mixture passageway 2 through a conduit H. A calibrated air inlet II is preferably provided for supplying air to the conduit I! to break the suction in the pasageway 2 on the conduit IT which might draw fuel from the pump chamber II. In the pump casing cover member there is a power cylinder I! and an atmospheric air bleed 2| to supply atmospheric pressure to the opposite side of piston II from the chamber It. In the cylinder ll there is a plunger 2| having its lower end 22 extending through and sealed in a central aperture through the member l2. The interior of the cylinder I! is in communication with the passage-' way 2 on the outlet side of the throttle valve! by means of a conduit 22 having a calibrated control port 24. Within the cylinder I! there is a helical coil spring 25 under compression and serving to force the member l2 downward through its discharged stroke upon opening move-- ment of the throttle valve but which is of such resilience that it will be compressed to permit th suction stroke of the member I 2 by subatmospheric pressure on the outlet side of the throttle valve 8.

Extending down from the bottom wall of the pump casing ii there is a supporting member 28 having an upper end wall 21 through which there is a guide aperture aligned with a guide aperture through the casing bottom wall and in alignment with the plunger 2|. Carried by the supporting member 28 there is a temperature responsive element or thermostat 28 preferably having a pressure responsive diaphragm 28 forming with the thermostat casing an expansible collapsible chamber in which there is a crystalline temperature responsive material 30 and a force conveying liquid ll. The material 30 may be any of the known crystalline materials which undergoes a change of state in the desired operating range such that it exerts a large positive force and has a high degree of expansion and contraction, such for example as is described in the patent to Vernet, 2,115,501, dated April 26, 1938. Interposed between the diaphragm 29 and the end plunger wall 22 and seating on the diaphragm 20 there is a rigid thrust rod 32 which has sliding flt through the openings in the end wall 21 and the bottom casing wall and packing material in serted therebetween. A. helical coil spring 22 within the supporting member 26 is held under compression between the end wall 21 and a head 34 on the rod 32 and serves to retract the rod upon contraction of the thermostat 28 and to maintain the rod in engagement with the thermostat diaphragm it.

The operation of this form of the invention shown in Fig. l is as follows: When the carburetor is connected to an internal combustion engine and the engine is operating at idle or low speed with the throttle valve d substantially closed, the subatmospheric pressure on the outlet side of the throttle valve will create a d'iflerential of pressure on the opposite ends or" the plunger ti so that the spring 25 will be compressed and the plunger it will have been moved from the position shown to its upward or suction stroire position. The diaphragm member it will have been moved upward by plunger ii to the limit of its suction stroke with the plunger end wall 22 out of abutting relation to the end of the thermostat thrust rod 32, the chamber it being filled with liquid fuel drawn thereinto from the float chamber through conduit it. Should the throttle valve ti now be moved toward open position for engine acceleration, the pressure in conduit 23 will approach atmospheric pressure so that the spring 25 will force plunger 29 and diaphragm member i2 downward through its discharge stroke which will discharge liquid fuel from chamber it] through the conduit ii into the mixture passageway 52. When the temperature to which the thermostat Ed is subjected, whether it is under bonnet ambient temperature or the temperature of the engine, reaches a predetermined temperature at which the fuel discharged into the passageway 2 will readily vaporize, the crystalline material 3d will undergo its change of state, thereby positively moving the thrust rod 32 upward. It will be apparent that upward movement of rod 32 will, on the down stroke of the plunger 2i, provide a rigid abutment for engagement by the plunger end wall 22, thereby positively limiting and obstruct ing the discharge stroke of the diaphragm mem ber id. The crystalline thermostat 2K5 exerts sufficlent resistance so that the spring 253 is ineflective to move the diaphragm member 62 upon engagement of thrust rod 32. The crystalline thermostat has an expansion curve which is substantially flat following the change of state of the crystalline material 3% and therefore when the desired operating temperature for the carburetor is reached, the quantity of fuel discharged from. the chamher it will remain substantially constant irrespective' of temperature increases above the desired operating temperature. The thermostat 23 will, of course, not lift the thrust rod Bil surficiently far to eliminate fuel discharge from the chamber 63 and therefore the member i2 will discharge the desired quantity of fuel into the passageway 2 when the throttle valve t is opened after the engine has reached its desired operating temperature.

Referring to Fig. 2, the carburetor has a casing is with a mixture passageway ti therethrough leading from a main air inlet Q2 and having a fuel air mixture outlet 53 for connection to the engine cylinders. In the passageway ll there is a converging diverging throat id such as a Venturi tube and discharging substantially at the throat there is a main fuel nozzle 55 fed with fuel from a constant level float chamber it. Within the float chamber tit there is a float operated inlet valve 'll controlling the admission of liquid fuel to the float chamber it and actuated by the float member ltl to maintain a subplunger end wall 22 with the u ciprocally asses so stantiallv constant fuel liquid level, say at the line L-L.

Positioned within the float chamber d8 there is a fuel pump Qt having a tubular cylindrical casing Ed in which there is slidably fitted a reciprocable fluid displacement member iii in the form of a hollow downward open piston. Positioned within the pump chamber 52 between the piston Fri and casing to there is a helical coil spring 53 which tends to move the piston 5i through its suction stroke. Through the end wall 53 of the casing lib there is a check valve controlled inlet bii leading from the float chamber 36 to the pump chamber 552. A piston rod 5 extends upward from the upper end of piston all and has a longitudinally extending discharge conduit 55% therethrough leading from the pump chamber 52. The upper end portion 56 is reof a fitting $7 which is carried by the casing 6%. An outlet checir valve 58 is provided in the con duit 55 to prevent back flow through conduit 55 into the pump chamber 52. The fitting Ell has its bore 59 discharging through a calibrated jet 6% into the passageway ti, an air bleed 6i being provided to supply atmospheric air to the bore 59 to break the suction 'eliect from passageway ll on the pump chamber 52. The air admitted by this bleed ti also aids in discharging the fuel from bore 59 into the passageway ii; The piston rod lid "extends through an opening in a covor plate 62 on the float chamber 56 and has an operating arm. $3 extending laterally therefrom.

In the mixture passageway ii there is a throttle valve 623 with an operating arm 65 extending from its shaft and connected by lost-motion linkage $6 to the rod arm 633. The linkage includes a pair of lever arms Si, 68 pivotally con dill nected to each other and to a supporting arm GE: by a common pivot pin it, the arm $9 extending from the casing to. The free ends of the levers til, 68 are connected by a tension spring ll so that free ends of the levers may move away from each other. A stop ii on the lever El is in the path of movement of lever 68 so that the movement of the levers toward each other by the spring ii is limited. The free end of lever Si is connected by a link it to the throttle arm 65. A link or thrust member i l connects the free end of lever 68 to the rod arm b3.

Extending downward from the bottom wall '65 of the float chamber as there is a tubular supporting member it having an aperture through its upper'end wall ll aligned with an aperture through the bottom wall it, which apertures are aligned with the piston rod 5 extending through and slidably fitting the aligned apertures and sealed therein against leakage of liquid by packing material there is a rigid thrust rod it having one end extending into the float chamber iii and supporting the casing to by engagement with the end wall 53% The other end of the rod 38 extends into the supporting member it and has, at its lower end, a head it. interposed between the end wall ll and the head it there is a helical coil spring 8b tending to move the rod downward. Carried by the lower end of the supporting member it there is a temperature responsive member 8! such as a crystalline material thermostat which ls similar to that described with respect to Fig. 1. Therefore, further description of the thermostat is unnecessary to an understanding of the operation of the same and the reference characters applied to Fig. l deslgnam like parts for this thermostat.

guided and suitably packed in the bore in Fig. 2 i as follows: When The operation of the form of invention shown the engine is operating in a cold condition, the thermostat and pump casing 50 will be in the positions shown so that upon opening movement of the throttle valve discharge of fuel from the chamber 52 will occur. When the temperature to which the thermostat 8| is subjected reaches the desired operating temperature for the engine, the crystalline material 30 will undergo its change of state, thereby moving the thrust rod 18 upward so as .to position the casing end wall 53 for abutting relation with the end of the pump piston 5| so as to positively obstruct its complete discharge stroke. The throttle valve 64 is permitted its full travel by reason of the lost-motion linkage 66 due to the stretching of spring II as the stop 12 moves away from lever 68. The thermostat 8| as above described with respect to Fig, 1 will only reduce the discharge stroke of the piston 5! when the engine is at its desired operating temperature.

Although the carburetors as shown are 01' the plain tube posterior throttle type it will be apparent that the invention is equally applicable to the anterior throttle type of carburetor or to the air-fuel proportioned type of carburetor.

Having thus described the invention, what is desired to be secured by Letters Patent of the United States is 1. In a carburetor, a casing having a mixture passageway, a throttle valve controlling flow through said passageway, a pump casing having a powercylinder communicatively connected tosaid passageway on the outlet side or said throttle valve, a plunger in said cylinder, a resilient diaphragm displacement member in said pump casing and operatively connected to said plunger, said pump casing and said diaphragm member forming a pump chamber having a fuel inlet and having an outlet leading to said passageway, a spring in said cylinder and operable to move said diaphragm member to discharge fuel from said chamber upon opening movement of said throttle valve, the wall of said pump casing having an opening aligned with said cylinder,a supporting member external of said chamber and extending from said wall, a crystalline material thermostat carried by said sup ortin member, and a rigid thrust rod operable by said thermostat and extending through said wall opening for engagement with said plunger to limit the discharge stroke of said diaphragm member.

2. A fuel supply pump for carburetors, comprising a pump casing, a reciprocal fuel displacement member in saidcasing and operable to discharge fuel therefrom, thrust means engaging one side of and operable to move said displacement member through its discharge stroke, a tubular supporting member rigidly secured to said casing and having its bore opening through the wall of said casing on the other side of said displacement member from and in -line with said thrust means, a rigid cup member rigidly secured to said supporting member and having its open side facing said bore, means movable by pressure and sealing said open cup member side, expansible thermostatic material in said cup member and operable on expansion to move said sealing means, and a thrust member-guided in said bore and seating on said sealing means and extending into said casing for abutting engagement with said displacement member, said thermostatic material variably positioning said thrust member to determine the length of the discharge stroke of said displacement member by said thrust means in accordance with temperature and holding said thrust member against movement by said thrust means.

WALTER, H. WEBER. 

